1. Field of the Invention
The present invention relates to a sheet feeding apparatus for feeding sheets from a sheet stacker.
2. Related Background Art
In a conventional large capacity sheet deck for transporting sheets on a transport path and feeding sheets to an image forming apparatus, a sheet transport speed is set at a high speed in order to maximize the image forming efficiency.
With a conventional sheet deck, a probability of error occurrence of the sheet separating operation increases as the transport speed becomes high. Upon occurrence of a sheet separating error, the image forming operation is intercepted, lowering the image forming efficiency.
On the contrary, if the sheet transport speed is lowered in order to reduce the probability of separation error occurrence, obviously the total image forming efficiency is lowered.
If the sheet separation operation is resumed under the same condition after a separation error, the succeeding separation operation is associated with a high probability of separation error.
In an image forming apparatus having a both-side mode for forming images on both sides of a sheet and a multiple mode for forming a plurality of images on the same side of a sheet, sheets are temporarily loaded in an intermediate tray during the image forming operation, and thereafter the sheets are again fed.
Also with such an image forming apparatus, if re-feeding from sheets from the intermediate tray is speeded up in order to improve the image forming efficiency per unit time, a probability of sheet separation error at the intermediate tray increases. The image forming operation is therefore intercepted, lowering the image forming efficiency.
On the contrary, if the sheet transport speed is lowered in order to reduce the probability of sheet separation error, obviously the total image forming efficiency is lowered. If the image forming operation is intercepted by an occurrence of separation error, the image forming operation already carried out prior to the error occurrence becomes wasteful. and Not only the sheet, but also expendables such as toner, ink and the like consumed during the image forming operation also becomes wasteful In addition, sheets remain on the intermediate tray so that the recovery operation of the apparatus becomes very complicated.